Light beam controls for color printing



Feb. 14, 1961 A. v. L. c. DEBRIE 2,971,447

LIGHT BEAM CONTROLS FOR COLOR PRINTING Filed Dec. 11, 1957 2 Sheets-Sheet 1 V/ R2 B j n i l J V B rnfi 2 F L :3

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LIGHT BEAM CONTROLS FOR COLOR PRINTING Filed Dec. 11, 1957 2 Sheets-Sheet 2 United States Patent 2,971,447 LIGHT BEAM CONTROLS FOR COLOR PRINTING Andre Victor Leon Clement Debrie, 111 Rue Saint- Maur, Paris, France Filed Dec. 11, 1957, Ser. No. 702,181 Claims priority, application France Dec. 21, 1956 9 Claims. (Cl. 95-73) The present invention relates to the printing of films in colour on printing machines in which the printing light is constituted additively by three beams of light passing through three coloured media, each of a primary colour, these coloured beams being each passed through a cylindrical lens in order that the outlines of these three beams are super-imposed on the surface of the printing window to re-constitute a white printing light adapted to each scene of the film to be printed by means of a pre-established correcting band obtained by known means and in which, for each scene, three neutral diaphragm filters control the composition and the intensity of the light.

If the light fromthe luminous source, an incandescent lamp for example, had a constant intensity and a constant colour-temperature, there would be no printing problem.

Unfortunately:

(1) The lamp varies in intensity, more or less rapidly, with use;

(2) During the same time, it varies in colour-temperature; and

(3) The optimum colour-temperature for each virgin film employed for printing is itself variable.

The invention overcomes these drawbacks by correcting the colour-temperature and the intensity of the light flux of the illumination obtained on the printing window, whilst retaining the proportions of the three basic colours given for each scene by the three filters of the pre-estab lished correcting band. In fact, there can be no question of constantly changing a correcting band, the preparation of which for the sequence of the scenes of the film to be printed is a considerable and exacting task.

With this object, the method which constitutes the invention consists, in a printing machine for films in colour, the printing window of which is illuminated with a printing light re-constituted by the super-imposition in the plane of the said window of three coloured beams, each of one primary colour, in causing each of them to pass through a filtering medium of appropriate tint; these three beams being each passed through a cylindrical lens in order that their outlines may be super-imposed over the entire surface of the printing window; each beam being controlled in intensity by a diaphragm filter of a correcting band, a group of three diaphragm filters being established for each scene on this correcting band which is interposed on the path of the three beams of light; in a machine of the kind referred to, in arranging on the path of the three beams of light three diaphragm devices, each of which regulates the intensity of one of these primary beams of light; in regulating each diaphragm by means having reference marks, in such manner that the proportion and the intensity of each flux of primary colour gives a correct print for a scene controlled by the correcting band, on the film utilised for printing; these elements being determined by photometric measure ments or by direct printing tests of the said scene, without changing the correcting band, by manual regulation of at least one of the diaphragms and, accessorily, by concomitant regulation of the voltage of the lamp which 7 Patented Feb. 14, 1961 is the source of light and of the said diaphragms; in choosing from the various prints, after treatment, the image for which the regulation is considered to be correct; in reestablishing this correct regulation on the printing machine by means of the reference marking of the diaphragms noted during the course of the tests; this correct regulation for the scene printed being thereby re-established; in effecting the printing of the whole band for which the light thus corrected will be adapted, scene by scene and automatically by the correcting band, in known manner.

In order to define the invention more clearly, it may be assumed for example that a scene is regulated by the correcting band, for the standard or reference light and the standard or reference film, with values of the elementary light beams controlled by the three diaphragm filters of the correcting band for the said scene, corresponding to values (arbitrarily selected in this case as an example) of:

1,000 units for the red beam, 800 units for the green beam, and 800 units for the blue beam,

the lamp being supplied from a -volt source.

After a certain time of working of the printing machine, when the aging of the lamp begins to take effect, it is found, for example, by measuring each beam with a photo-electric cell device, that the proportions are as follows:

1,000 units for the read beam, 600 units for the green beam, and 200 units for the blue beam,

the voltage on the lamp being always 110 volts.

By making use of photometric measurements, or by photographic control only, or by both methods, the values of the green and the blue are restored to their original values by the action of the diaphragms.

In order that this may be possible, it is essential that the initial values should comprise a certain degree of closure of the diaphragms, and the correcting operation will be carried out by opening those of the green and of the blue. Otherwise, the voltage at the terminals of the lamp will be increased and the following figures will then be obtained for the coloured beams for a voltage, for example, of 114 volts:

1,200 units for the red, 800 units for the green, and 800 units for the blue.

In this case, only the red beam will be stopped down by the diaphragm so as to bring it back to the value of 1,000 units, thus re-establishing in intensity and in colour temperature the effective illumination on the printing window.

It is generally by photometric measurements or by trial-and-error methods that the tests are made on the film printed with different settings of the diaphragms and, accessorily, of the electric supply voltage. The corrections having been marked for each print, the best image printed is chosen, after treatment, and the corrections of the light of the lamp are deduced in order to restore and adapt this light by the diaphragms to the virgin film used and to the source of light. In actual practice, these tests may be fairly rapid, the more so since the manufacturers of films frequently give for each batch of emulsion the trichromatic coefi'icients of sensitivity. The light thus regulated is applicable for automatic printing with the correcting band already established to control the whole of the scenes without being subjected to any modification.

This results in a very considerable saving in time and money.

By way of example and without any implied limitation, adevice for carrying the invention into effect is described and shown diagrammatically in the accompanying drawings.

Experience has shown that an adjustable diaphragm effecting the control of the luminous flux by symmetrical displacement, in the direction of the generator lines of the cylindrical lenses, of two screens which only permit the passage of one central adjustable band for each primary beam of light, enabled a uniform distribution of each coloured beam to be obtained on the surface of the printing window, the width of the central band controlling the light passing through the filter of the masking band and the corresponding lens, the latter having either a coloured filter attached to its plane face, or coloured throughout its mass, in known manner.

The device described employs diaphragms which pro duce these central bands of variable passage, but it is in no way described in any limiting sense, since the method can be adapted to any other suitably arranged diaphragmation.

Figs. 1 to 6 show individually six strips pierced with windows which control in pairs one of the primary beams.

Fig. 7 shows diagrammatically the unit comprising three control apertures set to different values in front of the unit of three cylindrical divergent lenses of a printing machine of known type (not shown).

Fig. 8 shows diagrammatically in horizontal crosssection the means of operation and an arrangement of two diaphragm bands, of the masking band, of the cylindrical lenses and of the printing window in a printing machine of which the other known members are not shown.

Fig. 9 is a section in side elevation of the displacement mechanism of the six diaphragms bands corresponding to Fig. 8.

In these figures, the same parts have been given the same reference numbers.

In Figs. 1 to 6, are shown the diaphragm bands A A B B C and C the windows of which 1 1 2 2 3 3 associated in pairs, close by sliding one against the other the passage of the corresponding beam of light before it passes through the cylindrical lenses L L and L which are stuck together.

These lenses are assumed in this case to be coloured throughout their mass: L in blue, L in green and L in red.

In Fig. 7, in order to avoid confusing the drawing, the correcting band has not been shown, nor has any guiding means or driving mechanism for the said diaphragm bands.

The diaphragm bands are made in the form of very thin strips of metal, of steel or in glucinum bronze for example, with their faces blackened, each carrying close to one extremity one of the various windows or cutouts, the shapes of which are shown at 1,, 1 2,,, 2 3,,, 3 with the straight closure or controlling portions 4,,, 4 5 5 6,, 6,, having a height suited to the beam to be cut-off and a contour which is generally rectangular, as in this case, but which may be of any shape, provided that it does not prevent at any moment the passage of the other beams of light. Towards their opposite extremities, the bands each comprise two long windows B1, B2, V1, V2 or R1, R2, placed one on the other, and a third shorter window aligned at one extremity with the two other windows Bl, B2, V'l, V2 or Rl, RZ, of equal lengths, this shorter window being followed near the extremity of the band, by a round hole 7a, 7b,.8a, 8b or 9a, 9b, having a diameter roughly equal to the width of the windows B1, B2, V1, V2, R1, R2, Bl, B2, V'1, V"2,'R'1, R'2. The holes 7a, 7b 3a, 8b, 9a, 9b, receive respectively fingers 11a, 115,12a, 12b, 13a, 13b, which 1 pass freely into the windows B1, B2, B'1, B2, V1, V2, Vl, V'2, Rl, R2 of the other strips when the latter are fixed together as shown in Fig. 7 and diagrammatically in Fig. 8.

The windows and the holes are superimposed at heights corresponding to the staging of the cylindrical lenses L Lv and LR.

These strips are given the necessary length so that they may preferably be deflected, for example at right angles towards the front and by the side of the vertical plane at right angles to the image window 10.

They are guided by achannel (not shown) which is fixed to the frame of the apparatus. Behind these strips, they are received one against the other in a compartment 15 of a mechanism casing 16 which, in an adjacent compartment de-limited by a partition 17, carries three similar shafts 18, 19 and 21 mounted one above the other and adapted to rotate between fixed stops, the shafts being threaded in opposite directions from their centres, and one which are mounted six movable nuts 22a, 22b, 23a, 23b, 24a, 24b, in pairs on the same shaft and constantly equidistant between each other and from the centre of the said shaft.

These nuts carry and have respectively fixed on them the fingers 11a, 11b, 12a, 13b, which are in this case fixed in the upper nuts at their lower portion, in the lower nuts at their upper portion and in the central nuts at their central portion.

These nuts may be of parallelepiped shape and slide between the wall of 16 and the partition 17.

The fingers pass through slots 25 25 and 25 in the partition 17, and through similar slots 26 26,, and

26 through the parallel face of the casing 16.

Through the compartment 15, the fingers pass through the windows of the strips and become engagedin their respective holes so as to carry the said strips along with them in longitudinal movement, the said strips varying the cross-sections of passage of the coloured beams, as shown in Fig. 7. In this case, the strips pass behind the masking band 20, the masking band being guided close to the flat rear face of the cylindrical lenses L L and L Because of the nearne'ss of the shafts and to avoid accidental movements due to projecting control knobs, the shafts 18, 19 and 21 are driven in rotation by a nonsymmetrical hollow prismatic key for example, which is fitted on the shaft to be moved, on its corresponding prismatic portion 18', 19', 21' which passes beyond the partition 27 of the front stop in the casing 16, the key being centered by a passage 28, 29 or 31 formed in an added base 32 of the casing 16 and keyed angularly in a single position on the shaft, carrying a graduated circular head which moves in front, of an index carried by the bottom 32. v i

In this way, the quantities can be marked by which each threaded shaft is rotated. The same key serves for all three screws, and is removed when the various adjustments haveall been effected, and that corresponding to the best print selected being re-established by virtue of the noted markings.

This casing 16 can readily be removed from the frame 30 of the machine in which it is fixed by passing its front portion 33 into a corresponding hole 34 of the casing 30, and by a flange 35 held by two screws 36 with large asymmetrical heads 37, which free or fix the said flange by rotation through less than (see Fig. 8).

*Inside the printing machine, the diaphragm strips are guided by elbowed guides into which they are pushed by placing the casing 16 in position. These guides have not been shown for the sake of simplicity of the drawing, their design being obvious.

Without departing from the scope of the invention,

I alternative constructions may be made of the devices for putting the present method into effect, the diaphragm bands could be planar, and their means of forwardor reverse movement may be controlled by means other than screws in two reversed portions, etc.

What is claimed is:

1. In a color-film printing machine including a light source forming three primary light beams of different primary colors, an arrangement for separately controlling the intensity of each of said primary light beams comprising, in combination, three rectangular diaphragms, each corresponding to and co-operating with one of the three primary colour beams constituting the printing light, each said diaphragm being formed by two co-operating thin elongated strips superimposed upon each other; a cut-out provided towards one extremity of each said strip, said cut-outs being formed in such manner that they allow the two other primary colour beams to pass freely at any opening value of the diaphragm considered; means for displacing said cooperating strips of each diaphragm longitudinally and respectively in opposite direction, whereby the light intensities of the primary colour beams cooperating with the said diaphragms may be individually increased or decreased at will.

2. An arrangement as claimed in claim 1, in which the six strips associated in pairs to form the three said diaphragms are arranged in juxtaposed relation, and are adapted to slide one with respect to the other.

3.1m a color-film printing machine including a light source forming three primary light beams of different primary colors, an arrangement for separately controlling the intensity of each of said primary light beams compising, in combination, three rectangular diaphragms, each corresponding to and co-operating with one of the three primary colour beams constituting the printing light, each said diaphragm being formed by two cooperating thin elongated strips; a window formed towards one extremity of each said strip; means for displacing said diaphragms longitudinally in front of at triple cylindrical lens unit of said machine; two elongated longitudinal parallel slots formed in the other extremity of each said strip; a third shorter slot formed parallel and adjacent the two elongated slots; and a hole formed in alignment with the said shorter slot, the shorter slot of each pair of strips being in transverse register when the strips are superposed, the said holes being formed adjacent opposite ends of said shorter slots; a pair of operating fingers adapted to engage in the holes of each pair of strips to efiect longitudinal movement of the strips thus engaged, while the longer parallel slots permit the passage and movement of the fingers controlling the displacement of the other two pairs of strips forming the other two diaphragms; two movable nuts adapted to actuate and to carry the said operating fingers which co-operate with the two strips of each diaphragm; a rotatable shaft threaded from its centre with oppositelyformed threads and adapted to engage and support the said movable nuts, said nuts being fixed for rotation and moving in opposite directions on said shaft, each threaded shaft being mounted parallel to the other two in a first compartment of a casing divided into two compartments by a longitudinal partition; a second compartment of said casing adapted to receive the six strips slidably guided with respect to each other, the operating fingers passing into and through said second compartment through elongated longitudinal slots formed in said partition and in the outer wall of said casing.

4. An arrangement as claimed in claim 3, in which said threaded shafts terminate at one extremity at the inner end of said casing, their other extremities extending beyond an inner end wall in which they are rotatably supported, said extended portions being each formed to receive a hollow key comprising a socket portion adapted for engagement in one fixed angular position on the driving extremity of each said shaft extension and a knurled plate-head provided with graduations and moving in front of an index fixed on said casing, one index -for each threaded shaft, whereby each of the three diaphragms can be regulated in turn by manual rotation of the corresponding threaded shaft by means of the said key.

5. An arrangement as claimed in claim 3, in which the said diaphragm strips are arranged inside the printing machine parallel over their entire length to the flat face of the cylindrical lens unit.

6. An arrangement as claimed in claim 3, in which the said diaphragm strips are guided inside the printing machine so as to follow a curved path with fiat end portions at right angles to each other, so that the said casing is mounted at right angles to the plane of the printing window of the said machine.

7. An arrangement as claimed in claim 3 in which the said casing has its inner extremity engaged in a corresponding passage formed in the frame of said printing machine and is retained by the engagement of asymmetrical screw heads engaging behind a flange rigidly fixed on the said casing.

8. In a color film printing machine including a light source forming three primary light beams of different primary colors, an arrangement for separately controlling the intensity of each of said primary light beams, in combination, three diaphragm means, each corresponding to and cooperating With one of the primary color beams, each of said diaphragm means being formed by two cooperating, elongated, thin strips, all of said strips having substantially the same width and being superimposed upon each other and each of the strips being formed with a cut-out therethrough, all of which are aligned in direction transverse to the elongation of said strips, each of said cut-outs having a controlling portion and at least one clearance portion off-set in trans verse direction with regard to the controlling portion of the respective strip, the controlling portions of said cutouts in the cooperating strips of each of said diaphragm means are respectively located in the path of different color beams and are aligned in longitudinal direction so that during relative movement of the cooperating strips of any one of said diaphragm means, the size of the color beams passing therethrough can be adjusted between a maximum size and zero, and the clearance portions in the strips forming one diaphragm means are off-set in transverse direction to the controlling portions of the cut-outs of the other diaphragm means and having in longitudinal direction of said strips such a length that the size of the color beam passing through the adjusted controlling portions of said one diaphragm means will not be affected by adjusting the position of the controlling portions of the other diaphragm means; and means for independently moving the cooperating strips of any one of the diaphragm means longitudinally and in opposite directions relative to each other.

9. In a color film printing machine, including a light source forming three primary light beams of different primary colors, an arrangement for separately controlling the intensity of each of said primary light beams, comprising in combination, three elongated diaphragms arranged superimposed to each other, each corresponding to and cooperating with one of the three primary color beams constituting the printing light, each of said diapragms being formed by tWo cooperating thin elongated strips superimposed upon each other and each of the strips being formed in the region of one end thereof with a cutout, the cooperating strips forming each diaphragm being longitudinally displaceable in opposite direction with respect to each other and the cutouts being formed in such a manner that during displacement of the cooperating strips cooperating with one of the primary color beams the intensity of the one primary color beam may be increased or decreased while the two other primary color beams may pass freely through the cutouts, each of said strips being formed in the region of the other end with a hole and at least one additional cut out; and means for displacing said cooperating strips of each diaphragm longitudinally and respectively in oppr'm'ite direction, said means compri sing a pair of operating fingers adapted to engage respectively in the holes of each 5 cooperating pair of strips to effect longitudinal movement of the strips thus engaged, and said additional cut outs are arranged to permit the passage and movement of the fingers controlling the displacement of the other two cooperating pairs of strips forming the other two of 10 said diaphragms.

References Cited in the file of this patent UNITED STATES PATENTS Gregory Ian. 23, Jones May 17, Jones n July 5, Williams Aug. 28, Evans Oct. 16, Terwilligerv Mar. 23, Deb'rie Jan. 15, Debrie Feb. 5, 

